Fault Tolerant Control Against Actuator Failures of 4WID/4WIS Electric Vehicles

A fault tolerant control (FTC) approach based on reconfigurable control allocation for four-wheel independently driven and steered (4WID/4WIS) electric vehicles against driving motor failures is proposed in order to improve vehicle safety, performance and maneuverability after the driving motor failures. The proposed fault tolerant control method consists of the following three parts: 1) a fault detection and diagnosis (FDD) module that monitors vehicle driving condition, detects and diagnoses actuator failures; 2) a motion controller that computes the generalized forces/moments to track the desired vehicle motion using model predictive control method; 3) a reconfigurable control allocator that optimally distributes the generalized forces/moments to four wheels aiming at minimizing the total tire usage. The FTC approach is based on the reconfigurable control allocation which reallocates the generalized forces/moments among healthy actuators once the actuator failures is detected. If one or more driving motors fails, the FDD module diagnoses the actuator failures. Then the reconfigurable control allocator accommodates faulty driving motors and reconfigures the control allocation law of the healthy motors to achieve the desired vehicle motion to the greatest extent. Numerical simulations have been conducted to verify the proposed algorithm. It has been shown from the simulations that once the driving motor fails, the fault tolerant controller ensures the desired vehicle motion. Compared to the PID controller, the fault tolerant controller prevents the deviation after actuator failures occur, improving the post-fault safety, performance and maneuverability of the 4WID/4WIS EVs.